In several industries, and in particular the food industry, there is a need to separate liquid greases, fats and oils from waste water prior to passing the waste water to the sewage system. The waste water could be, for example, discharged from a washing device for cleaning dinnerware and cooking utensils, from floor drains and mop sinks. If the greases and fats solidify in the sewage system, a blockage can occur which is expensive to remediate.
It has been found that the liquid wastes from kitchens are often immiscible mixtures of water and oils. As is well known, a first immiscible liquid of one specific gravity will float on a second immiscible liquid having a greater specific gravity. It has also been experimentally determined that the general kitchen waste oils have a specific gravity of about 0.92-0.93, whereas the specific gravity of water is about 1.0. As such, the kitchen oils float on top of the waste water.
Some municipalities require that separators be able to treat effluent mixtures of immiscible liquids from floor drains, floor mounted mop sinks, and the like. Some floor-mounted immiscible liquid separators are not adapted for treating effluent liquids from such equipment. These liquid separators are often equipped with ball-type float valves that require daily cleaning, and thus such type of separators cannot be used as in-ground separators, as it would be very troublesome to gain daily access to the ball-type float valves and clean them. Also, this type of immiscible liquid separator requires frequent internal access to remove the particulate matter that has settled to the bottom of the separators, thus requiring easy access to the internal areas of the separators.
U.S. Pat. No. 7,297,284 by Owen et al., discloses various embodiments of immiscible liquid separators. Described therein are parameters that are important when considering the construction of a separator to separate the oil content from the water content of a waste liquid. Two immiscible liquids of different specific gravities will separate under the force of gravity into two separate layers in a calculable or measurable time period, according to Stokes Law. Typical immiscible liquid separators are constructed with a separation chamber of sufficient size to allow the waste liquid to separate therein, with the oil floating on top of the water. As more waste liquid is added to the separator, the floating oil rises and overflows via an oil outlet into an oil reservoir. The previously separated water flows from the separation chamber under a separator plate into a water chamber where, when the level is sufficiently high, the separated water overflows over a fixed height linear weir and out of the separator. The linear weir spans the distance between the opposite sides of the separator enclosure. If the mixture of two immiscible liquids is introduced into the separation chamber at a known flow rate, then the chamber can be sized to ensure that separation is completed before the heavier liquid (water) flows under the separation plate to the separated water chamber. A ball-type float valve is employed to prevent surges of separated water from flowing upwardly into the oil reservoir. The disadvantage of using a ball-type float valve is that it often requires daily maintenance to clean it and prevent floating deposits from allowing water to pass with the oil through the valve.
In the prior art immiscible liquid separators, the weir is often a planar plate that extends laterally between sidewalls of the separator. Thus, when waste liquid influents enter the separator and are separated, the separated water flows over the weir and exits the separator and is drained away via the water drainage system. The separated water flows over the linear weir much like excess flood water flows over a spillway, dam or levy.
Immiscible liquid separators can be employed in restaurants, and the like, and are often mounted on the floor under the sink or wash basin drains. The separated oil must be watched carefully so that the reservoir does not become full or overflow. In the event that the facility produces a substantial amount of immiscible waste liquids, then either the oil reservoir of the separator must be drained more often, or a larger oil reservoir must be provided.
From the foregoing, it can be seen that a need exists for an immiscible liquid disposal system which handles a variable quantity of immiscible liquid mixtures, and does not require a ball-type float valve. This can be accomplished by having a long-length weir that handles a wide range in volumes of separated water, without requiring a large foot print for the separator.